1. Field of the Invention
The present invention relates to an ink jet head to be mounted on an ink jet printer. Further, the present invention relates to a connecting sheet and a composite sheet to be used in the ink jet head. Moreover, the present invention relates to a method of manufacturing the ink jet head and the composite sheet.
2. Description of the Related Art
Ink jet printers are well known. An ink jet printer is provided with an ink jet head that discharges ink. The ink jet head is provided with a plurality of nozzles, a plurality of pressure chambers, and a plurality of actuators. Each nozzle is communicated with a corresponding pressure chamber. Each pressure chamber is coupled with a corresponding actuator. When one of the actuators is activated, pressure is increased of ink housed in the corresponding pressure chamber coupled with the activated actuator, and the ink is discharged from the nozzle communicated with this pressure chamber.
The plurality of actuators is provided with, for example, one piezoelectric sheet. This piezoelectric sheet faces the plurality of pressure chambers. One common electrode is formed on a first face of the piezoelectric sheet, and extends over the plurality of pressure chambers. A plurality of individual electrodes is formed on a second face of the piezoelectric sheet. Each individual electrode corresponds to one of the pressure chambers in their positional relationship. When a driving voltage (a driving signal) is applied to one of the individual electrodes, an electric field is generated between that individual electrode and the common electrode, and the portion of the piezoelectric sheet disposed between the individual electrode and the common electrode contracts. When the piezoelectric sheet contracts, there is a change in the volume of the pressure chamber coupled with the individual electrode. As a result, pressure (discharging energy) is applied to the ink within the pressure chamber. A conventional ink jet head is taught in Japanese Laid-Open Patent Application Publication No. H11-334061.
One of a plurality of signal lines is connected to a corresponding individual electrode in order to apply the driving voltage thereto. Each of the individual electrodes has an input terminal connected therewith in order to connect the signal line to the individual electrode. The ink jet head taught in Japanese Laid-Open Patent Application Publication No. H11-334061 uses a wired sheet on which are formed a plurality of output terminals and a plurality of signal lines that transmit driving voltage. Each output terminal is connected to a corresponding signal line. In this ink jet head, each output terminal formed on the wired sheet is connected directly to a corresponding input terminal.
A surface face of the wired sheet is covered by an insulating film. The insulating film can be formed with a solder resist film, for example. The insulating film covers the plurality of signal lines. A plurality of holes is formed in the insulating film at locations corresponding to the output terminals of the wired sheet. Each output terminal is exposed in a different corresponding hole. Since the output terminals formed on the wired sheet are not covered by the insulating film, these output terminals can make contact with the input terminals.
Since the plurality of signal lines of the wired sheet is covered by the insulating film, there is no short circuiting between these signal lines even if ink splashes or dust adhere to the wired sheet. A technique pertaining to this is taught in Japanese Laid-Open Patent Application Publication No. H10-256688.